ABSTRACT

Permian strata within the Western Canada Sedimentary Basin are preserved in a narrow belt in the Front Ranges throughout most of the Eastern Cordillera, but owing to truncation beneath several sub-Mesozoic disconformities, they are absent from the subsurface, except in the Peace River Embayment. The Permian succession, which is generally thin but laterally persistent, consists of marine, supratidal to basinal siliciclastics and silty to sandy carbonates. It lacks major basinal shale accumulations and well defined continental deposits. These rocks are referred to as the Ishbel Group, which is subdivided into several formations that generally conform to the boundaries of at least three transgressive-regressive sequences. Biostratigraphic data, obtained mainly from occurrences of conodonts, brachiopods, and foraminifers, are used to date these sequences.

Oil and gas plays are generally restricted to structural and stratigraphic traps where rocks of the Belloy Formation are involved in fault-bounded structures in the Peace River Embayment; proven oil reserves account for about 2 per cent of the total for the Western Canada Sedimentary Basin. The Belloy Formation consists of three informal members: lower carbonate, middle sandstone, and upper carbonate. The thickness of the Formation varies from a zero edge in the east to more than 200 m near the Foothills. Isopachs demonstrate northwestern trends related to facies distribution, which appear to parallel pre-Belloy or syndepositional blockfaulting trends, with carbonates developed on the highs. Phosphate is common in parts of the Permian succession, but does not appear to be of immediate economic value.

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